Treatment of hydrocarbon gases



Fatentea May 5, H936 TREATMENT OF HYDROOARZBON GASES- Jacque C. Morrell, Chicago, 11]., assignor to Universal Oil Products Company, Chicago, 111., w corporationof Delaware No Drawing. Application August 31, 1932,

Serial No. 631,178

9 Claims. (01. 196-10) This invention relates to the treatment of hydrocarbon gases and refers more particularly to the treatment of the gases formed in cracking the heavier portions of petroleum oils with the primary object of producing gasoline fractions therefrom though the process may alsobe applied to the treatment of other gas mixtures of generally similar character, 1. e., those containing unsaturated or olefin hydrocarbons.

In a more particular sense the process is concerned with the transformation of'the more reactive constituents of such gas mixtures, to wit, the olefins, into liquid products which may be used as constituents of gasoline so that the overall yield of motor fuel from the cracking process is increased. Gases originating from a cracking process may be treated directly or after removal of the hydrogen sulfide contained therein. The' gases to be treated by the process may be produced by subjecting natural or other hydrocarbon gases to elevated temperatures and pressures to crack them and increase their content of un-.- saturated hydrocarbons.

In cracking heavy hydrocarbon oils to produce lower boiling fractions, the yield of gasoline is limited by the fact that as more severe conditions particularly of temperature and time are imposed, the gas and coke yields increase but of proportion to the yield of gasoline and a point may be reached where the gasoline yield actually decreases while that of the less desirable products, gas and coke, sharply increases. Apart from their use as fuel, the gases resulting from cracking operations have heretofore been looked upon as an undesirable by-product so that a process for increasing the yield of desired gasoline fractions and at the same time decreasing the yield of gas will have economic value.

In one specific embodiment the present invention comprises the treatment of gases from cracking plants with heavy metal salts, zinc chloride, aluminum chloride, tin chloride, etc. alone or in combination with halogen acid such as hydrogen chloride and other similar compounds functioning as polymerizing agents to controllably produce polymers from the olefins in the gases, such polymers being of a character suitable for use as constituents of gasoline, particularly to improve the antiknock value thereof. The present process is particularly directed to the production of high antiknock motor fuel or blending agents therefor. The salts may be employed as such or in solution. Water vapor or steam may be added to assist the reactions in some instances.

It isparticulariv pointed out that the various salts themselves or their compounds with halogen acids, water, etc. may produce different results with respect to yield and quality of product and are therefore not equivalent to each other. The

selection of a salt or combination of salts will 5 depend upon the conditions of treatment and the results desired.

. The composition of the gases from cracking processes varies over wide ranges in respect to paraflins and oleflns and sulfur derivatives of 10 hydrocarbons, the composition depending upon thetype of charging stock cracked and the severity of cracking conditions. The following analysis is typical of the gases produced in the cracking of heavy distillates and resides in 15 present day commercial plants.

duces the highest yields of desirable liquid prod ucts.

. According to the process of the present invention gases from cracking processes are treated with polymerizing agents, particularly zinc 40 chloride and/or other metal chlorides such as those of aluminum, tin, iron, etc. which have a similar though not equivalent action, under conditions most conducive to the formation of dimers and trimers of the olefins.

In one method of operation the oleiln-con- 45 hydrochloric acid when the latter is employed 55 may be controlled to produce maximum percentages of dimers and trimers and arrest more extensive polymerization reactions so that the formation of high molecular weight complexes of a gummy and resinous character is minimized. The process may be carried out at ordinary temperatures and pressures but preferably elevated temperatures and superatmospheric pressures are employed, the conditions chosen being regulated by the nature of the gases undergoing treatment and the products desired. Aqueous solutions of zinc chloride may also be employed, preferably adding controlled quantities of steam or water to the solution when operating at elevated temperatures.

Obviously no entirely general rules can be laid down for obtaining the best results in all cases, not only because of the variations in the percentage of olefins but also on account of variations in the types of olefins as to whether they are normal or iso compounds and because of the variation in the relative proportions of these diflferent types. However, a consideration of the general mechanism of the reactions furnishes some guidance for predetermining the best conditions of operation in any case though the exact T deteirmination of conditions is usually a matter of tria As exemplifying the type of reaction which results in the formation a dimer from a monoolefin, the case of isobutylene may be considered. When isobutylene is treated with hydrochloric acid and zinc chloride using a relatively large amount of the zinc chloride, say by weight of the isobutylene, varying percentages of di-, triand tetra-butylene are formed. There is evidence to support the assumption that hydrochloric acid when employed adds directly to isobutylene to form a butyl chloride which then by water, which may account for the observed I PIESSUIES.

reacts with further amounts of sio-butylene to form an octyl chloride as an intermediate product, this decomposing with loss of hydrochloric acid to form octylene, thus allowing the hydrochloric acid to react further in the same cycle.

There is evidence also in support of the view that intermediate addition compounds are formed between olefins and zinc chloride, a compound of this character having the formula CsHm-ZZnClz, being formed by the direct addition of one molecule of amylene to two of zinc chloride. Such compounds are readily decomposed fact that arcertain amount of moisture is desirable to insure the desired polymerization reactions particularly when using zinc chloride. Whatever the exact course of the reactions may be it is nevertheless an observed fact that liquid products boiling within gasoline range and possessing unusually high antiknock value can be produced from the olefins in cracked gases by the use of zinc chloride or other polymerizing and oondensing agents of the same character.

While elevated temperatures are sometimes desirable, the temperature used must not be high enough to cause too extensive polymerization. In some cases it suiiices to merely pass the gases from an oil cracking process over a composite contact mass or to bubble the gas mixture through a stationary pool of concentrated zinc chloride solution, at ordinary temperatures'and In other cases elevated temperatures 'and pressures a e desirable and where the time of contact is properly regulated even molten salts may be employed.

. The gases may be upwardly so that thorough contact is eifected. In this case the hydrocarbon liquids formed will flow along with the treating solution and be recovered as an upper layer in a subsequent receiver or separating tank from which the chloride solution may be recirculated back over the top of the tower to effect further treatment. When the gases are passed through a solid contact mass comprising a carrying or contact substance and a metal salt, some of the polymers formed will gradually flow down and be recovered from the bottom of the tower and some will be carried along in the stream of gas to be later recovered in absorption equipment. When the gases are bubbled through stationary pools of solutions of polymerizing salts, the desired polymers will form as an upper layer which may be continuouslyor intermittently withdrawn from the system.

Control of the extent and action of the polymerizing reactions may be to some extent a matter of adjustment of the amount of moisture and hydrochloric acid present. In the operation of the process moist hydrochloric acid or hydrogen chloride may be injected into the stream of gases, or either hydrochloric acid or water may be introduced into treating equipment so that aqueous hydrochloric acid is present as a liquid phase, or hydrochloric acid may be a constituent of the polymerizing salt solution in any desired quantity.

An example of results obtainable by the use parts by weight of finely divided pumice contain-' ing adsorbed thereon one part by weight of commercial zinc chloride. The gas mixture may be saturated with water vapor and contain in addition a small percentage of hydrochloric acid" tgas, say, about 0.3% by volume of the gas mixure.

By this operation there may be recovered from two to two and one-half gallons of 50' A. P. I. gravity liquid boiling within the range of: 150 to 400 F. and consisting for the most part of hexylenes, octylenes and decylenes and some higher homologs, resulting from the formation of dimers from the corresponding oleflns of one-half their molecular weight. The resulting liquid product may have an octane number or antiknock value exceeding that oi benzol. In the case under discussion the gasoline yield may be increased from a total of 60 to 66% by the incorporation 01 these polymers with the gasoline normally produced from the cracking process. Furthermore, owing to the high antiknock value of the polymers, the

octane number of the gasoline may be increased of the process may be given in connection with 1 This gas, produced at a rate of vantage. Good results may be obtained with zinc process containing 35% of olefins, approximately '3 gallons of liquid product of high antiknock value may be obtained per thousand cubicfeet of gas. The antiknock value of the liquid thus obtained frequently exceeds that of benzene and is highly desirable as a motor fuel blending agent. Other conditions of temperature and pressure may be employed, the yield being somewhat reduced in this particular case; at ordinary temperatures and pressures. Goodresults may also be obtained with other salts or solutions thereof such as tin chloride, etc.

The examples given herein are merely illus-' trative of the many possibilities of the process and are not to be considered as limitations thereof. a

I claim as my invention:

1. A process for the treatment of gaseous hydrocarbons containing olefin hydrocarbons, which comprises subjecting the gaseous hydrocarbons in the presence of an added hydrogen halide and in the absence. of any substantial quantity of normally condensable hydrocarbon vapors to the action of a metallic salt in aqueous solution.

2. A process for the treatment of gaseous hydrocarbons containing olefin hydrocarbons, which comprises subjecting the gaseous hydrocarbons in the presence of an added hydrogen halide and in the absence of any substantial quantity of normally condensable hydrocarbon vapors to the action of a metallic salt in aqueous solution at an elevated temperature.

3. A process for'the treatment of gaseous hydrocarbons containing olefin hydrocarbons, which comprises subjecting the gaseous hydrocarbons in the presence of an added hydrogemhalide and in the absence of any substantial quantity of normally condensable hydrocarbon vapors to the action of a metallic salt in aqueous solution at an elevated temperature and superatmospheric pressure.

4. A process for'the treatment of gases containing olefin hydrocarbons to produce antiknock motor fuel or blending agent therefor, which comprises subjecting the said gases in the presence of an added hydrogen halide and in the absence of any substantial quantity of normally condensable hydrocarbon vapors to the action of an aqueous solution of a metallic salt at elevated temperatures and superatmospheric pressure.

5. A process for the treatment of gases containing olefin hydrocarbons to produce antilmock motor fuel or blending agent therefor, which comprises subjecting the said gases in the presence of an addedhydrogen chloride and in the absence of any substantial quantity of normally condensable hydrocarbon vapors to the action of an aqueous solution of zinc chloride at elevated temperatures and superatmospheric pressure.

condensable hydrocarbon vapors to the action of an aqueous solution of zinc chloride.

7. A.process for the treatment of gases from a cracking process to produce high antiknock motor fuel or blending agent therefor, which comprises subjecting the said gases in the absence of any substantial quantity of normally condensable hydrocarbon vapors to the action of an aqueous solution of zinc chloride in the presence of added hydrogen chloride. I

8. A process for the treatment of gases from a cracking process to produce high antiknock motor fuel or blending agent therefor, which comprises subjecting the said gases in the absence of any substantial quantity of normally condensable hydrocargon vapors to the action of zinc chloride in the presence of added hydrogen chloride and water vapor.

9. A process for the treatment of oleflnic gases to polymerize the gaseous olefin hydrocarbons and convert the same into liquid hydrocarbons, which comprises subjecting the said gases in the absence of any substantial quantity of. normally condensable hydrocarbon vapors to the action of an aqueous solution of zinc chloride in the presence of added hydrogen chloride.

JACQUE C. MORREIL. 

